1. Field of the Invention
The invention relates to a sheet processing apparatus, which can receive, sheets discharged from an image forming apparatus such as a copying machine, a printer, a facsimile apparatus or a compound machine, or a business machine, and can carry out a so-called bookbinding process.
Also, the invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile apparatus or a compound machine, and particularly to an image forming apparatus capable of incorporating thereinto a sheet processing function such as the bookbinding process of forming a sheet bundle and saddle-stitching the sheet bundle, and thereafter folding the sheet bundle in two, compactly and in light weight and in a custom-made fashion.
2. Description of the Related Art
There has been put into practical use a sheet processing apparatus which can carry out a so-called binding process of receiving sheets discharged from an image forming apparatus such as a copying machine, a printer or a facsimile apparatus one by one and forming a sheet bundle, and stapling (saddle-stitching) the formed sheet bundle on its fold line, and folding (bundle-folding) the stapled sheet bundle in two on its fold line into a brochure, and outputting and stacking the brochure.
It is often the case that this sheet processing apparatus capable of carrying out the bookbinding process is arranged on the downstream side of an image forming apparatus main body for forming an image on a sheet. In some types of the image forming apparatus, the sheet processing apparatus capable of carrying out the bookbinding process is integrally contained or connected as a purchase option (so-called option).
Also, many of sheet processing apparatuses capable of carrying out the bookbinding process can select and execute one of several processing menu such as the so-called end binding process of stapling one end of a formed sheet bundle, the simple stacking process of simply stacking sheets one by one without forming a sheet bundle, and the punching process of forming holes for filing in a sheet or a sheet bundle.
Japanese Patent Application Laid-open No. H6-72064 discloses a recording apparatus, which can selectively effect side stitching and saddle stitching by a single stapler. The recording apparatus can stack sheet bundle at a common position, and effect the flat binding at the common position, and effect the saddle stitching by moving a sheet bundle by a predetermined amount from the common position.
In a sheet processing apparatus shown in Japanese Patent Application Laid-open No. H10-279163. An exclusive processing unit for carrying out the bookbinding process is disposed below a universal processing unit capable of carrying out the end binding process and the simple stacking process, and one of these processes can be selected and executed.
In a sheet processing apparatus shown in Japanese Patent Application Laid-open No. 2001-72310, a two-fold mechanism for folding a sheet bundle in two is disposed on the inner part side of a processing tray for receiving sheets one by one and forming a sheet bundle, and the saddle stitching process in the bookbinding process is carried out by the use of a stapling device for carrying out the end binding process.
A sheet processing apparatus shown in Japanese Patent Application Laid-open No. 2003-241578 has a discharging path for conveying a two-fold sheet bundle to a position at which it flatly overlaps simply stacked sheets, and a sheet bundle subjected to the bookbinding process is stacked on a fixed exclusive stack tray through this discharging path.
In an image forming apparatus shown in Japanese Patent Application Laid-open No. 2001-72311, below an image reading apparatus (scanner apparatus), there are disposed an image forming portion contained in the plane of the image reading apparatus and using a photosensitive drum, a processing tray for forming a sheet bundle, and a vertically movable stack tray, and the trailing edge side of a sheet bundle formed by sheets being stacked on the processing tray is stapled, thereafter the sheet bundle is discharged from the processing tray onto the stack tray and stacked on the latter.
Of course, there has also been put into practical use an image forming apparatus in which below an apparatus main body of a common specification for forming an image on a sheet, various sheet cassette units formed into the same planar outline and side appearance as the apparatus main body are connected together, whereby the processing capability in a wide sense is made changeable.
In recent years, in order to save the installation space of an image forming apparatus including a sheet processing apparatus, and increase the degree of freedom of the layout of the interior of a room around the installation space, the downsizing of the image forming apparatus including the sheet processing apparatus has been desired, and as shown in Japanese Patent Application Laid-open No. 2001-72311, there has been commercialized an image forming apparatus in which the number of possible sheet processes is reduced to thereby make the in-body discharge of a sheet bundle possible.
However, in the image forming apparatus wherein the in-body discharge is effected, the full height of the apparatus is suppressed and yet, a stacking space for sheets and sheet bundles is secured in the plane of the apparatus and therefore, the disposition space for a mechanism in the sheet processing apparatus is limited, and it is impossible to additionally dispose an exclusive processing unit for carrying out such a bookbinding process as shown in Japanese Patent Application Laid-open No. 2001-72310.
Yet, it greatly spoils the commercial value of the image forming apparatus to provide only the exclusive processing unit for carrying out the bookbinding process, which is merely a convenient additional function to an ordinary user, and eliminate the requisite end binding process unit.
So, as shown in Japanese Patent Application Laid-open No. 2001-72310, there has been proposed to carry out the saddle stitching process in the bookbinding process by the use of a stapling apparatus for carrying out the end binding process of a sheet bundle, and in this case, the number of the stapling apparatuses is saved, but a space for move a large sheet before folded in two greatly in a horizontal direction becomes necessary in the machine body and therefore, the length and installation area of the sheet processing apparatus become still greater than those of the sheet processing apparatus shown in Japanese Patent Application Laid-open No. H10-279163.
Also, two-fold sheet bundles are stacked on a stacking place discrete from a vertically movable type stacking tray on which end bound sheet bundles are stacked and therefore, if the stack tray is carried on a sheet processing apparatus which effects the in-body discharge, the full height of the sheet processing apparatus cannot be suppressed, and if two stacking places are forcibly secured, each stacking place becomes narrow and the full load condition occurs earlier and thus, the taking-out of the sheet bundle is effected frequently.
Also, with the above-described sheet cassette as the reference, it has been proposed that below an apparatus main body of a common specification, various sheet processing apparatuses formed into the same plane outline as the apparatus main body be superposed and connected, but when the stacking space for each kind (size) of discharged sheets and sheet bundle is heaped, the full height becomes great, and in the first place, it is not easy to optimize the form and disposition of the stacking space for sheet bundles, for example, a method of taking out the sheet bundle.
In recent years, however, in accordance with an improvement in the color print accuracy of image forming apparatuses, there have been increasing opportunities for preparing presentation materials, and preparing materials in a brochure shape including photographs, and if the bookbinding process can be incorporated into an ordinary sheet processing apparatus capable of carrying out the end binding process, the commercial values of the sheet processing apparatus and the image forming apparatus will greatly heighten and further, if the number of parts thereof can be suppressed to thereby construct the apparatuses compactly and in light weight and at low prices, a great demand for the image forming apparatus can be aroused.